A new clean approach for production of cobalt dihydroxide from aqueous Co(II) using oxygen-reducing biocathode microbial fuel cells

Cobalt recovery from aqueous Co(II) is one critical step for recovery of cobalt and recycle of spent lithium ion batteries, but suffers from consumption of large amount of energy and chemicals. Effective and environmental friendly processes are thus needed to improve the existing process limitations. This study proposes a new approach for cobalt dihydroxide production using oxygen-reducing biocathode microbial fuel cells (MFCs) with respect to aqueous Co(II) utilization and clean production. OH^- generated from oxygen-reducing biocathodes in situ reacted with Co(II) to form precipitated Co(OH)₂, achieving cobalt dihydroxide production with simultaneous electricity generation. The highest cobalt recovery rate of 0.079 ± 0.001 mmol/(L·h) and cobalt dihydroxide yield of 0.24 ± 0.00 mol/mol COD with simultaneous electricity production of 1.5 W/m³ were obtained under the optimal condition of a dissolved oxygen of 0.031 mM, an initial pH of 5.6, and an initial Co(II) concentration of 0.508 mM. These results demonstrate that cobalt dihydroxide production from aqueous Co(II) using oxygen-reducing biocathode MFCs may be a promising process for recovery of cobalt and recycle of spent lithium ion batteries as well as power generation.